The present invention relates to a process for preparing cyclic and/or polymeric compounds by metathesis of starting materials that contain at least two functional groups in the form of substituted or unsubstituted alkene or alkyne units.
For the purposes of the present invention, the term xe2x80x9cmetathesisxe2x80x9d refers to a mutual transalkylidenation of alkenes and alkynes in the presence of catalysts. Reactions of this type are employed in many industrially important processes. A review may be found in: M. Schuster, S. Blechert, Angew. Chem. 1997, 109, 2124 and S. Armstrong, J. Chem. Soc., Perkin Trans. 1, 1998, 371. Metathesis reactions include the oligomerization and polymerization of acyclic dienes (ADMET) and the synthesis of carbocycles and heterocycles having various ring sizes by ring closing metathesis (RCM). Crossed metatheses of different alkenes are also known (Brxc3xcmmer, O. et al. Chem. Eur. J. 1997, 3, 441).
For the above-mentioned metathesis reactions, it is possible to use the ruthenium-alkylidene compounds described in WO-A-93/20111, the ruthenium-based catalyst systems described by A. W. Stumpf, E. Saive, A. Deomceau and A. F. Noels in J. Chem. Soc., Chem. Commun. 1995, 1127-1128, or the catalyst systems described by P. Schwab, R. H. Grubbs and J. W. Ziller in J. Am. Chem. Soc. 1996, 118, 100 (see also WO 96/04289) as catalysts.
The use of nonaqueous ionic liquids for metathesis reactions has recently been described. These ionic liquids are salts or mixtures of salts that are liquid over a wide temperature range. The advantage of ionic liquids is that they are immiscible with aliphatic hydrocarbons. In organic reactions for which the use of a catalyst is necessary, heterogeneous catalysis can be achieved by addition of ionic liquids and a suitable catalyst that dissolves only or preferentially in the ionic liquid.
U.S. Pat. No. 5,104,840 describes the use of such mixtures as solvents for transition metal complexes, especially nickel complexes that contain no carbon-nickel bonds.
EP-B-448445 describes the use of ionic liquids for the dimerization of unsubstituted monoolefins using nickel chloride. However, a disadvantage here is the use of organoaluminium halide, especially the pyrophoric dichloroethylaluminium, for preparing the ionic liquid.
U.S. Pat. No. 5,525,567 describes the use of ionic liquids for the disproportionation of unsubstituted monoolefins using tungsten catalysts. Here too, it is necessary to use an organoaluminium halide, preferably the pyrophoric dichloroethylaluminium, for preparing the ionic liquid.
EP-A-882691 describes the use of ionic liquids for the dimerization of unsubstituted monoolefins in the presence of nickel chloride. Apart from the pyrophoric dichloroethylaluminium that is used here too, a further disadvantage is that the excess of the Lewis acid aluminium chloride in the ionic liquid results in an acidic reaction mixture.
The above-described metathesis processes are, moreover, suitable only for the reaction of unsubstituted monoolefins, i.e. very simple organic molecules. These processes are not suitable for the reaction of multiply substituted starting materials bearing functional groups, since the catalysts described there cannot be employed or the ionic liquids are unsuitable for other catalysts because of their composition or the fact that the reaction mixture has an acidic character.
It is an object of the present invention to provide a universally usable process for the metathesis of starting materials that contain at least two functional groups in the form of alkene or alkyne units that is carried out using ionic liquids. The process should also be able to be used for substituted alkenes or alkynes.
The invention, meeting the above-named object, provides a process that subjects starting materials that contain at least two functional groups in the form of alkene or alkyne units to metathesis. The process is carried out using ionic liquids. Advantageously, the process can be used for substituted alkenes or alkynes. These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and appended claims.
We have found a process for preparing cyclic and/or polymeric compounds by metathesis of starting materials that contain at least two functional groups in the form of substituted or unsubstituted alkene or alkyne units in the presence of one or more homogeneous or heterogeneous catalysts, wherein the metathesis is carried out in the presence of ionic liquids and the catalysts used are transition metal carbenes or transition metal compounds that form transition metal carbenes under the reaction conditions or transition metal salts in combination with an alkylating agent.
It has surprisingly been found that the presence of ionic liquids in the metathesis reaction of starting materials that contain at least two functional groups in the form of substituted or unsubstituted alkene or alkyne units leads to an increase in the operating life of the catalyst since it can be used in the ionic liquid for further metathesis reactions.
In a preferred embodiment, the present invention makes it possible to prepare carbocyclic or heterocyclic compounds having ring sizes of xe2x89xa75 ring atoms, including medium-sized rings (from 8 to 11 ring atoms) and large rings (xe2x89xa712 ring atoms) and/or polymeric compounds that can be homopolymers, copolymers or block copolymers.
In ring closing metathesis reactions, the ring-closure reaction competes with polymerization. If this reaction is carried out using starting materials that contain at least two functional groups in the form of alkene or alkyne units, it results in mixtures of cyclic compounds and polymers.
The formation of cyclic compounds is favoured by carrying out the reaction in organic solvents at high dilution or by addition of relatively large volumes of ionic liquids. This applies particularly to the preparation of medium-sized rings (from 8 to 11 ring atoms) and large rings (xe2x89xa712 ring atoms).
The large reaction volumes of organic solvents required to achieve the necessary high dilution limit the maximum space-time yields. Separating off the products after the reaction is complete requires time-consuming separation operations such as chromatography and usually leads to irreversible deactivation of the catalyst used.
The use of relatively large volumes of ionic liquids does, however, allow the desired products to be separated off easily, since they are present in the organic phase that is not miscible with the ionic liquid. If a catalyst that dissolves exclusively or preferentially in the ionic liquid is selected, the deactivation of the catalyst after the work-up can be avoided and the phase comprising the ionic liquid and the catalyst can be used for further metathesis reactions.
In the process of the invention, preference is given to using starting materials that contain, apart from the functional groups participating in the metathesis reaction, at least one further substituent that is inert in the metathesis reaction and/or a heteroatom. These substituents or heteroatoms can be selected independently from among: branched or unbranched alkyl radicals, aromatic or nonaromatic carbocyclic rings, carboxylic acids, esters, ethers, epoxides, silyl ethers, thioethers, thioacetals, anhydrides, imines, silylenol ethers, ammonium salts, amides, nitriles, perfluoroalkyl groups, geminal dialkyl groups, alkynes, alkenes, halogens, alcohols, ketones, aldehydes, carbamates, carbonates, urethanes, sulphonates, sulphones, sulphonamides, nitro groups, organosilane units, metal centres and oxygen, nitrogen, sulphur and/or phosphorus-containing heterocycles.
The process of the invention is particularly preferably carried out using, as starting materials, xcex1,xcfx89-dienes that may contain at least one further substituent that is inert in the metathesis reaction and/or a heteroatom. These substituents or heteroatoms may be selected independently from among branched or unbranched alkyl radicals, aromatic or non-aromatic carbocyclic rings, carboxylic acids, esters, ethers, epoxides, silyl ethers, thioethers, thioacetals, anhydrides, imines, silylenol ethers, ammonium salts, amides, nitrites, perfluoroalkyl groups, geminal dialkyl groups, alkynes, alkenes, halogens, alcohols, ketones, aldehydes, carbamates, carbonates, urethanes, sulphonates, sulphones, sulphonamides, nitro groups, organosilane units, metal centres and oxygen-, nitrogen-, sulphur- and/or phosphorus-containing heterocycles.
In particular, the process of the invention is carried out using, as starting materials, xcex1,xcfx89-dienes that bear a substituent NRR1 in the xcex1 position to a double bond, wherein
R is an organic substituent, preferably hydrogen, fused or unfused aryl, alkyl, CN, COOR2 or halogen,
R1 is tert-butyl, P(R)2, P(R2)2, COR, SO2PhR, COOR or CONRR2,
R2 is alkyl or phenyl,
R and R1 together form 
xe2x80x83and said xcex1,xcfx89-dienes may also bear at least one further substituent R in any other position in the molecule with the exception of the xcex1 position. Use of these dienes as starting materials in the process of the invention makes it possible to obtain cyclic and/or polymeric compounds that bear a substituent NRR1, wherein R and R1 are as defined above, in the xcex1 position to the double bond.
In a particularly preferred embodiment, the above-mentioned xcex1,xcfx89-dienes are compounds of the formula (I) 
wherein R, R1 and R2 are as defined above and
n is 1, 2, 3 or 4, preferably 1 or 2, particularly preferably 1.
When using compounds of the formula (I), the process of the invention preferably gives cyclic compounds of the formula (II), 
wherein R, R1, R2 and n are as defined above and the double bond may also be substituted by at least one radical R, and/or polymeric products.
Starting materials that are very particularly preferably used in the process of the invention are diallylamine or 3-amino-1,7-octadiene, particularly preferably in their N-carboxymethyl-protected form, or 1,7-octadiene, 10-undecenoyl-allylamide, 1,4-bis-oxypropen-2-yl-but-2-ine or buten-4-yl 10-undecenoate.
It is also possible to use mixtures of starting materials in the process of the invention. In this case, the starting materials can be added as a mixture to the reaction medium or else can be added sequentially to the reaction medium.
In the process of the invention, the catalysts or catalyst precursors used are transition metal carbenes or transition metal compounds that form transition metal carbenes under the reaction conditions or transition metal salts in combination with an alkylating agent. These catalysts can be either ionic or nonionic.
The process of the invention is preferably carried out using catalysts of the formulae (III) to (VI), wherein M is ruthenium or osmium, preferably ruthenium. 
R3 to R7 are radicals that can be selected independently from among hydrogen, C1-C20-alkyl, C3-C8-cycloalkyl, C2-C20-alkenyl, C2-C20-alkinyl, C6-C18-aryl, C1-C20-carboxylate, C1-C20-alkoxy, C2-C20-alkenyloxy, C2-C20-alkinyloxy, C8-C18-aryloxy, C2-C20-alkoxycarbonyl, C1 -C20-alkylthio, C1-C20-alkylsulphonyl or C1-C20-alkylsulphinyl, N-aryl; in each case unsubstituted or substituted by C1-C12-alkyl, perfluoroalkyl, halogen, C1-C5-alkoxy or C6-C18-aryl. The radicals R3 to R7 may be linked to one another in cyclic compounds.
X1 to X3 are anionic ligands that may be selected independently, in particular Fxe2x88x92, Clxe2x88x92, Brxe2x88x92, CNxe2x88x92, SCNxe2x88x92, R3Oxe2x88x92, R3R4Nxe2x88x92, (R3-R7)-allylxe2x88x92, (R3-R7)-cyclopentadienylxe2x88x92, wherein the radicals R3 to R7 are as defined above.
L1to L3are uncharged ligands that can be selected independently, in particular CO, CO2, R3NCO, R3R4Cxe2x95x90CR5R6, R3Cxe2x89xa1CR4, R3R4Cxe2x95x90NR5, R3Cxe2x89xa1N, R3OR4, R3SR4, NR3R4R5, PR3R4R5, AsR3R4R5, SbR3R4R5, wherein the radicals R3 to R5 are as defined above;
m is1 or2.
Particularly preferred catalysts or catalyst precursors are compounds of the formulae (III) and (IV) in which L1 and L2xe2x95x90PR3R4R5, where R3 to R5 are as defined above and very particularly preferred radicals of this type are aryl or alkyl, in particular secondary alkyl radicals or cycloalkyl radicals.
Very particular preference is given to using the following compounds as catalysts in the process of the invention: 
where Cy=cyclohexyl, iPr=isopropyl, Ph=phenyl.
The catalysts can be used in isolated form or can be generated in situ in the reaction medium from catalyst precursors. The amounts of catalyst that are used in the process of the invention are generally from 0.001 to 15 mol %, based on the starting materials. The process of the present invention is preferably carried out using from 0.1 to 12 mol % of catalyst, particularly preferably from 0.5 to 9 mol %, based on the starting materials.
The ionic liquids used in the process of the invention are salts or salt mixtures that are liquid in a temperature range from xe2x88x9220xc2x0 C. to 300xc2x0 C.
In the process of the invention, preference is given to using ionic liquids that comprise aluminium halides in combination with at least one quaternary ammonium halide and/or at least one quaternary phosphonium halide.
As quaternary ammonium compounds, particular preference is given to using heterocyclic compounds that contain at least one nitrogen atom. These are, for example, pyridinium compounds or imidazolium compounds.
Very particularly preferred ionic liquids are aluminium chloride in combination with 1-methyl-3-butylimidazolium chloride, 1-methyl-3-ethylimidazolium chloride, N-butylpyridinium chloride and/or tetrabutylphosphonium chloride.
The process of the invention is preferably carried out using ionic liquids that comprise a combination of aluminium halide and quaternary ammonium halides and/or quaternary phosphonium halides in a molar ratio of (0.6-1):1. The molar ratio of aluminium halide to quaternary ammonium halide and/or quaternary phosphonium halide should never be greater than 1 since otherwise an excess of Lewis acid is present in the reaction mixture. This acidic reaction mixture leads to deactivation of the transition metal carbene catalysts.
Preference is also given to using ionic liquids that comprise ammonium hexafluorophosphate, ammonium tetrafluoroborate, ammonium tosylate or ammonium hydrogen sulphate or consist of ammonium hexafluorophosphate, ammonium tetrafluoroborate, ammonium tosylate or ammonium hydrogen sulphate in the process of the invention.
Ionic liquids used are particularly preferably pyridinium hexafluoro-phosphate, 1-methyl-3-butyl hexafluorophosphate, pyridinium tetrafluoroborate, pyridinium hydrogen sulphate or N-butylpyridinium hexafluorophosphate.
As ionic liquids in the process of the invention, it is also possible to use combinations of aluminium halide with mixtures of quaternary ammonium halides and/or quaternary phosphonium halides, or mixtures of ammonium hexafluorophosphates, ammonium tetrafluoroborates, ammonium tosylates or ammonium hydrogen sulphates.
The process of the invention can be carried out in the presence of one or more additives, preferably a solvent, that, for example, makes it easier to separate the products from the ionic liquid and the catalyst present therein. In the presence of an additive and the ionic liquids, a heterogeneous catalyst system is obtained when ionic catalysts or catalysts that dissolve preferentially in the ionic liquid are used. After the metathesis reaction is complete, the ionic phase comprising the catalyst can easily be separated from the additive and the reaction product present therein. The catalyst in the ionic liquid can be used for further metathesis reactions without intermediate purification steps.
Such additives can be selected, for example, from among: phosphorus compounds, amines, perfluorinated compounds, metal alkoxides and organic solvents. Suitable organic solvents are, in particular, halogenated hydrocarbons such as dichloromethane, trichloromethane, tetrachloromethane, 1,2-dichloroethane or trichloroethane, aromatic compounds such as benzene, toluene, xylene, cumene or halogenobenzenes, alkanes such as pentane, hexane or cyclohexane, esters such as tert-butylmethyl esters or acetic esters, ethers such as diethyl ether, tetrahydrofuran and dimethoxyethane, amides such as dimethylformamide, antioxidants such as hydroquinones, acetone, dimethyl carbonate or alcohols.
Preferred additives for use in the process of the invention are C5-C20-alkanes, ethers and halogenated hydrocarbons.
Pentane, n-hexane, methyl tert-butyl ether or dichloromethane are very particularly preferably used in the process of the invention.
The process of the invention is preferably carried out at pressures in the range from 0.1 to 10 bar, particularly preferably at atmospheric pressure. However, the process of the invention can also be carried out at subatmospheric pressures down to 0.01 bar and superatmospheric pressures up to 100 bar.
The process of the invention is usually carried out in a temperature range from xe2x88x9220xc2x0 C. to 200xc2x0 C., preferably from 0xc2x0 C. to 150xc2x0 C., very particularly preferably from 20xc2x0 C. to 100xc2x0 C.
The cyclic compounds or polymers that can be prepared by the process of the invention can be further purified and processed with the aid of customary methods. The catalyst in the ionic liquid can be used for further metathesis reactions without intermediate purification steps.